Double-acting hydraulic piston shock absorber



July 21, 1953 c. GRANET ET AL 2,646,136

DOUBLE-ACTING HYDRAULIC PISTON SHOCK ABSORBER Filed Jan.' 9, 1950 y 3 Sheets-Sheet 1 5 Sheets-Sheet 2 FIGA C. GRANET ET AL DOUBLE-ACTING HYDRAULIC PISTON SHOCK ABSORBER r 5 E 2 W M G f M H W a M 9 .a 8 E .5 2 6 \H3 55, m 7 2 3 4 3 2 11:14h IYIIIWWU 5 a OKI ...H7 1 v k a fr., L HHH... Ml iw July 21, 1953 Filed Jan. 9, 195o July 21 1953 c. GRANET ETAL 2,646,136

DOUBLE-ACTING HYDRAULIC PISTON SHOCK ABSORBER Filfed Jan. 9, 1950 5 Sheets-Sheet 5 Maze; 4a/5 Patented July 21, 1953 DOUBLE-ACTING HYDRAULIC PISTON SHOCK ABSORBER Charles GranetCourbevoie, and Maurice Helbig,

Paris, France Application January 9, 195o, serial No. 137,616

In France January 22, 1949 9 Claims. (Cl. 18S-88) dustry for the suspension of bodyworks, of hydraulic double-acting piston shock-absorbers comprising a body secured to one of the springinterconnected elements and forming a horizontal cylinder, in which a double-acting piston is movable from' one to the other side of an intermediate transverse plane under the action of a rocking finger carried by a pivot shaft provided with an external lever yconnected with the other element.

. The present invention has for its object to provide improvements in shock-absorbers of that type, which considerably simplify manufacture thereof and make it possible to obtain low cost prices, while at the same time improving the conditions of operation, both as concerns the centering of the sliding piston and the wear therein, as well as the shock-absorbing effect in both directions of the pistons displacement.

According to a feature of the invention, the piston, provided with symmetrical heads, comprises within each head a check-valve adapted to suck in reserve liquid toward the end of the cylinder, while the return of the liquid from both ends of the cylinder to the supply is eiected through a common duct provided with a single loaded return-valve, said duct connected with channels provided with check-valves formed in the body and connecting said duct with the ends of the cylinder.

According to another feature, the piston is formed of a free-cut steel tube partitioned by seating discs for the intake valves and their springs. Y

According to another feature, the piston is traversed from end to end by a rod coaxial with the cylinder serving as a guide for the intake valves and supported at its ends by plugs sealing the ends of the cylinder.

Like the majority of known shock-absorbers,

. said apparatus starts producing its damping effect .at the very start of the pistons stroke, the braking action at once assuming a value predetermined by the load of the return valve, with however the following peculiarity, viz that since said valve is common to the return of the liquid from both ends of the cylinder, the braking produced by that pressure remains the same regardless of the direction of the stroke.

It has 'been attempted, as is known, to cause the braking or retarding force to vary throughout the stroke in order to confer greater flexibility to the suspension; and devices are known which allow attenuation of the retardation in the vicin- ,j

2 ity of the position of balance, until the time the piston has moved by a ycertain amount corresponding with a substantial deection of the suspension springs. It is known however that the balance position is variable depending onV the greater or lesser degree to which the suspended vehicle is loaded and the reciprocations of the piston are eifected about this Variable position of balance. In order to maintain the same damping effect from any balance position wherever the latter may be, it has been suggested to control the reduction in pressure at the start by means of a slide-block free to move parallel with the axis of the cylinder and maintained in stable position by pressures `exerted on both ends of said slide-block and corresponding at each cylinder end, with the integral of the variable pressures that prevail at that end of the cylinder.

The present invention also has for its object to provide a shock-absorber comprising a device of such type, which makesit possible to suppress the braking action during normal outward strokes while restoring it during the return strokes, and impart to it a reduced value in the vicinity of the position of equilibrium, and adapted to conform itself to any variations in said position.

l According to another feature of the invention, the axial rod in the cylinder-gis shorter than the cylinder, so as to be slidable in its supports secured to the end plugs under the action of the pressure prevailing in the space at the ends of said rod, in communication with the cylinder end throughmetered leakage orifices, and it is provided with collars forming annular leakage passages for the liquid between the rod and the intake valve throughout the major portion of the permissible piston stroke from its position of balance. At the ends of the free-cut portions of the rod, forming the annular leak passages, transitional leak passages are formed by obliquely extending cuts in the end shoulders of the freecut portions.

Further features and advantages of the device will appear from the ensuing description of one form of embodiment of a shock-absorber according to the invention, given merely by way of example and illustrated in the appended drawings, in which:

Figure l is a side elevational view of the shockabsorber;

Figure 2 is a plan view, cover removed;

' Figure Slisa longitudinal vertical section on line III- III of Figure 2;

Figure 4 isa view in horizontal section on line Figure 'i is a vertical section of the shock-k absorber through the axis of the cylinder, in a modified embodiment;

Figure 8 is a transverse section taken on line VIII-VIII of Figure 7.

Reference will first be had to yFigures l to 6 of the drawings.

According to the exemplary embodiment selected and illustrated the shock-absorber body which is a casting, preferably of light metal (see Figs. l to 3), forms a cylinder i, bored through from end to end, sealed at both its ends by screw plugs 2 and communicating through an open part 3 in its intermediate portion into an enlarged cavity 4 which is provided with a cover 5 retained by two screws-6 seated against synthetic rubber washers i.

in the cylinder bore there is mounted a doubleaotingpiston which, according to an essential feature of the invention, is constituted by a free-cut steel tube 8 provided with transverse partitions.

The external free-cut reduces the diameter of the intermediate or central portion and leaves at the ends two piston heads 9 sliding in the bore. On its side toward the opening 3, the tube 3 has at the midpoint of its length a wide cut-out iii throughout almost half its diameter (also see Figli). Both piston-heads Si are symmetrically related to each other. To either side of said cut-out, the inner wall of the tube is bored over a short distance to receive a lwasher il forming a transverse partition. Against that face of said washer which is directed` toward the cut-out, is applied a thick synthetic rubber washer i2 provided vvith a socket or bushing i3 formed with an obliquely-cut lat i4 toward the mouth oi the opening 3.

Against the outer face of the washer ii is applied a synthetic rubber intake-valve i centred on 9. rod i8 which `traverses the piston from end to end and is mounted axially of the cylinder. The rod iS is carried'at each end in a long synthetic rubber Iboss il maintained against the end face of the plug Z'by a metal washer I8 surroundingly engaging its tapered contourA and clamped bythe plugagainst a synthetic rubber gasket I9 preventing leakage through the screw-threads.

Each intake-valve i5 is applied against the partition Il which serves as a seating therefor, by means of a spring .26 applied against a perforate washer 2i (also see Fig. 6) retained by lugs punched therein, within a circumferential groove of the piston 9.-

The body is laterallyenlarged with a cylindrical mass 22 having its axis parallel to the axis of the cylinder i and provided with 'a duct for the return of the liquid from both ends of the cylinder towards thel reserve supply provided by the enlarged cavity` fi. Said duct has two symmetrical branches and a common portion. Each branch of the duct (see Fig. 4) comprises an obliquely extending channel 23 which may be cast integrally and which extends from a recess 24 -formed at the end of the cylinder bore to open into a bore in the cylindrical mass 22. Said bore which is formed in several steps or decreasing diameter, comprises at its outer end an enlarged portion 25 sealed by a screw-plug 26 provided with a gasket ring 21 of synthetic rubber. At the inner end of the enlarged portion a metal ring 28 with a small central aperture is presstted. Against the internal face of this ring and in the next following intermediate portion 29 is seated a square block of synthetic rubber 30 (also see Fig. 6) forming a check-valve, applied against the ring serving as a seating therefor by means of a spring 3l. The latter is confined in said portion 29 as a result of the positioning of the ring 23 and bears against the inner end of said intermediate portion and the corners of the square check-valve. The spring is one of low strength which enables the check-valve to be lifted for a small pressure; the valve merely serves the function of a check-valve. The innermost step oi the bore is a short small-diameter hole 32 which opens into that part of the return duct which is common to both ends of the cylinder.

Said common portion oi the duct essentially comprises a vertical bore 34 in a cylindrical mass 33 of the body, perpendicular to the cylindrical mass 22 (see Figs. i and 5). Said bore 3l! the outward opening of which is sealed by a screw plug 35 provided withv a synthetic rubber gasket ring 35, contains a spring-loaded valve which constitutes the single return valve. The bore is extended by a bore 3'! of lesser diameter communicating with an integrally-cast channel which opens into the enlarged cavity li. In bore 3'! of smaller diameter is iitted a shouldered bushing or socket 39 whose shoulder is seated against a gasket ring lil) at the end of the larger diameter perforation. Said bushing is a hard t with the valve, for which it serves as a seat. Said valve opens towards the channel 38 and comprises a head M resting against the smaller end of the bushing and a cylindrical shank formed with a longitudinal hole 43 and a transverse hole lili beneath the head i. it is threaded at its other end and receives a crimped-on annular nut 45 which serves as a seat for a valve-spring i6 retained against said Y annular nut and the bushing 3Q.

Between both bushings i3 of the piston (Figs. 3 and 5) and on each side oi the central rod iii there is engaged a nger i'i having its end rounded as at iS to control the displacements of the piston. Sairjl ngers could be produced by milling a unitary element. They are limited in their displacements by beads 49 of the body deiining the opening 3 while such displacement is made possible, as shown in Fig. l, as a result of the flats provided on said bushings. The two identical parallel fingers are mounted with spacers El@ on a splined portion iii oi a shouldered spindle 52 rotatable in bosses 53 and 5d of the body, on an axis perpendicular to the cylinder. @n one side, said spindle projects through a sealing gasket formed by a synthetic rubber ring 55, moulded so as to form a iiexible annular iiange 5E bearing against the spindle at its point oi egress and retained in a metallic casing 5i, which enables it to be presstted into a complementary recess oi the body. The projecting part of the'spindle presents a splined journal portion 5s and terminates in a threaded end 52 designed to receive a lock-nut for a connecting lever secured to the splined journal and controlling the shock-absorber.

On the opposite side the body comprises bearing bosses corresponding with two bolt-holes 5l extending through it from end to end and a securing lug 62.

Alugs into the grooves A The operation is immediately comprehensible. In the reciprocating shock-absorbing movements,

should the operating ngers which normally oc- V cupy a vertical position, slant towards the left of Fig. 3 to the position shown, the right-hand end of the cylinder becomes lled with liquid. The Ylatter passes from the supply cavity 4 through the bushing I3 and the partition IIV which forms a seat for the intake check-valve I5, raises said check-valve and enters into the related end of the cylinder through the perforate disc 2 I. At the other end of the cylinder, the compressed liquid (see Fig. 4) escapes through the recess 24, the oblique channel 23 and the stepped bores 25, 29, 32, raising thebored out in a lightweight metal body, the piston is formed by machining a highly resistant treated steel tube, the friction coelncient of which against the light metal is low. Moreover, the axial rod I6 for centering the intake valves I5 being mounted in synthetic rubber bosses and the valves themselves being made of synthetic rubber, no impacts between metals are to be feared. Said rod is not in contact with the'piston. The movements of the latter is controlled by the fingers 41 without any play owing to the thrust from the resilient blocks formed by the bearing or seating washers I2 for the bushings I3, which provide a slight clamping action upon the rounded extremity 48 of said fingers. The symmetrical insures a perfectly symmetrical action on the piston and the latter slides in the cylinder without any danger of jamming.

As for the simplicity of assembly, this is manifest.` Machining the piston is reduced to a freecutting operation, a single' milling step being necessary to form the cut-out I0. ,The springseating washers 2I (Fig. 3) `are put into position by means of a pressing operation which attens out said washers, initially dished, to engage their provided therefor. The the intake valve I5, the bearing the resilient blocks I2 provided with4 their bushings I3, are inserted and positioned through the cut-out I0. In the same way, the check-valves (Fig. 4) are very simple to mount. The Spring 3l and valve 30 are inserted, and the ring 28 serving as a seat for it is pressfitted in. The loaded valve is put into place in a similar fashion by press-fitting the bush 39 in which said valve is mounted. Finally, the sealing gasket 55 for the control spindle is presented ready for assembly in its metal casing 51, which it is simply necessary to press-fit into the corresponding recess. After the piston has been springs 29 and partitions II,

' mounted, the control fingers 41 are inserted into the body through the upper opening of the cavity Il, the cover 5 of which has been removed; they are then engaged into the piston and mounted on the control spindle by insertion of the latter.

In the. alternative embodiment illustrated in arrangement of the latter in twoplanes equidistant from the axis,`

Figures'l and 8, the rod I6 supported at its ends by two centering parts blocked in the end of the cylinder bore by the plugs 2, is substantially shorter than the length of the cylinder and is freely mounted in said centering parts, so as to be capable of motion on both sides from its intermediate position. The small chamber 63 formed in the centering part at each end of the rod communicates through a metered leakage port with the chamber 64 deiined by the piston at the corresponding end of the cylinder. Such leakage may, for example,-simply result from a minute amount of clearance systematically provided between the rod and the centering part I1.

At the level of each piston head, the rod I6 presents 'a free-cut section 65 extending over a certain llength towards the cylinder end from the bearing face of the intake valve, when the piston and rod occupy the intermediate position shown in Fig. 7. At the ends of `said free-cut portion, cutfouts 66 and 61 having cross-sectionstapering down in both directions further provide transition leakage ports. Y

Each cylinder end communicates, as described in the r'st exemplary embodiment, with a longitudinal perforation 68 communicating at its centre with a common return channel 69 leading to the supply. On either side of said channel, each branch perforation sealed by a screw-plug 10 formed with a pin 1I, contains a sliding valve formed by a cylindrical part 12 having a central hole 13, applied against the pin 1I by a spring 14. The common return channel 69 contains the spring-loaded valve 15 which is the single return valve previously described with reference to Figs. 1-6 and opens through a channel 16 into a groove 11 in the central part of the bore so as to communicate with the supply 4.

The device operates as follows:

Assume the rod I5 is in its intermediate position, as well as the piston-controlling lingers 48, for the balanced condition of the suspension. A deflection ofthe springs will rotate the ngers 48 say clockwise, moving the piston toward the left of Fig. 1. Assume further that the amplitude of the reciprocation is restricted.

As soon as vthe piston departs from its position of balance the intake valve I5 is located fully above the free-cut section 66 of the rod and opens up an annular leakage duct, which prevents the pressure from building up at the left-hand end of the cylinder. No braking action is produced during the outward stroke, if the amplitude is insuiiicient for the left-hand face of the valve I5 to reach the end of the free-cutsection 65. During this stroke the intake valve I 5 of the right pistonhead is raised, allowing the liquid to re-enter the chamber 64 at the right-hand end of the cylinder.

In the return movement of the piston toward the right, the left-hand intake valve I5 may remain seated, the liquid sucked in passing through the leak-way in the free-cut portion 65. Said leakway is shut down as the piston again passes through its position of balance, but the cut out 66 still permits of a reduced leakage, which avoids a sudden re-opening movement of the intake valve. In the chamber 64 of the right-hand end of the cylinder, on the other hand, the liquid pressure builds up from the very start of the return movement, up to a value corresponding to the loading of the return spring of valve 15, until the yright-hand intake valve I5 passes over the righthand free-cut section B5 of the rod at the time the piston crosses its equilibrium position. The

ypressure therefore again -becomes zero during the outward'stroke toward the right, `as previously described, and will only re-assume a retarding value corresponding with the spring-loading on the return valve during thereturn stroke towards its position of equilibrium.

The pressure-variations at both ends of the cylinder do not at once make themselves felt in the little chambers 63 at the ends of the rod, since thoseV chambers are only connected with the chambers `Sil through metered leakage ports. On the other hand, the pressure which becomes established in any one of said chambers at the end of `a certain lapse of time is a, pressure which corresponds with the integral, over said time, of the pressure variations in the adjacent chamber 64. When the position of balance of the suspension corresponds with the intermediate position of the piston shown in Fig., 7, the integrated pressures in both small end-chambers 63 are equal and the rod occupies the intermediate position shown.

Assume now that the balance position of the shock-absorber is varied, and undergoes say a displacement towards the left of Fig. 7, the rod i6 first remaining in its intermediate position shown. During the pistons outward strokes, as stated, the annular l'eakway prevents retardation and the latter will only occur during the return strokes which correspond to the displacement of one of the intake valves over the central full-diameter portion ofthe rod I6. Now the assumed leftward displacement of the equilibrium position increases the length of said displacement for the right- .hand valve i and reduces it for the left-hand valve l5. It follows that the braking pressure persists a longer time in the right-hand than in the left-hand chamber 6d.

rjhe pressure in the small right-hand chamber 83 will therefore soon be higher than in the chamber 63 at the other end of the rod and will cause a displacement of the latter as far as a `position'symmetrical with respect to the new position of balance, this restoring similar conditions of symmetrical damping as in the event where the position of balance was the intermediate position shown in Fig. 1.

t will thus` be seen that the rod I6 Will of its own accord place itself in a position symmetrical to the equilibrium position wherever the latter may be.

As shown, the free-'cut portions 55 are only provided with a length limited to a given distance from the ends of the cylinders. This arrangement is for the Vpurpose of ensuring retardation at the end of the outward stroke, when, as a result of a violent shock, the suspension assumes a large displacement. Returning again to a description of the operation, it will be assumed, for example, that at the end of the pistons leftward outward stroke, the intake valve l5 at the left-hand side runs past the end of the lefthand freecut portion 55.v The annular leakway is then sealed oi and the pressure in the lefthand chamber Sli quickly rises to a value as given by the springloading of the return valve. A violent bumping of the suspension is thus avoided in the event of a brutal impact.

The cut-out 67 of the rod provided a transition between non-braking and braking, which averts a brutal stop of the displacement. At the beginning of the return stroke, it gradually promotes the leakage and avoids a brutal return of the intake valve I5 upon its seat, said Valve rising as soon as the movement is initiated but dropping back again upon opening of the annular leakway.

The-shocki-.absorber as just described therefore providesfor -a freedeflection of the springs and only damps the back-to-balance return movements, thereby allowing the suspension to retain all of its ilexibility, inasmuch as damping is only produced atthe end of the high-amplitude deiiection strokes in the event of violent shocks to prevent or restrict bumping. Its operation moreover is very smooth owing to the transitional leakage means, its assembly, as shown, is very economical, and the rod I6 may be prepared for its slide-valve function by a most simple machining step on said rod.

As will be understood, the invention is not limited to the shock-absorber illustrated and described, similar structural improvements being applicable to shock-absorbers of different design.

What we claim is:

l. A double-acting piston shock-absorber comprising in combination a body having a bore extending through the same forming a pistonreceiving-cylinder, said body having a central cavity communicating with said cylinder intermediate the ends of said cylinder and serving as a liquid supply reservoir, a piston in said cylinder formed with heads adapted to slide in said cylinder on each side of said cavity, a shaft extending through said cavity in a -direction transverse to the axis of said cylinder, an acting nger on said shaft engaging said piston, plugs sealing the external ends of said cylinder and forming end chambers in front of the iston heads, said heads having openings and valve means controlling the opening for intake of liquid from said central cavity to said end chambers, a return duct formed of two branches opening at the cylinder ends and a common part opening in said cavity, check-valves in said lbranches and a spring-loaded return valve in the common part of said duct.

2. A shock absorber according to claim 1, comprising further in combination for each branch of said returny duct a bored portion, a screw plug sealing the external end thereof and formed with an internal projecting pin, a channel between the cylinder end and said bored portion opening laterally to said pin, a ring of resilient material sliding in said bored portion, and a spring urging said ring towards said pin in a closed position checking any return of liquid toward said cylinder end.

3. A shock-absorber according to claim 1, comprising further in combination for the common part of said return duct a bored portion, va screwlplug sealing the external end thereof, a channel between the bottom of said bored portion and said central cavity, a bushing press-tted in said bored portion` and opening into said channel, a valve formed with a head adapted to seat on the inner face of said bushing and a hollow shank slidable in said bushing and bored transversely beneath said head, a washer xed on the end of said shank and a compression spring around said shank between said bushing and said washer.

4. A shock-absorber according to claim 1, comprising further in combination for the piston, a steel tube having a bored mid-portion forming end. shoulders and a central wide cut-out over nearly half of its diameter between end portions forming heads of said piston, perforated partitions with peripheral lugs engaging an internal groove of said heads, washers against said shoulders in the bore mid-portion, block of resilient ,material forming in each head an intake-valve .seating against said Washer, a spring between g said perforated partition and said valve thick rings of resilient material against said washers in said bored mid-portion, bushings mounted on said rings, and said acting nger being formed with a rounded end clamped between said bushings.

5. A double-acting piston shock-absorber, comprising in combination, a body having a vbore extending through the same forming a piston receiving-cylinder, said body having a central cavity communicating with said cylinder intermediate the ends of said cylinder and serving as a liquid supply reservoir, a shaft extending through said cavity in a direction transverse to the axis of said cylinder, plugs sealing the external ends of said cylinder, an axial rod .supported at both ends lby said plugs, a piston including a steel tube having a central wide cutout between Vend portions forming piston heads, an inner partition with a central opening around said rod in each head, an outer perforated partition around said rod, an intake valve formed n 0f a block of resilientV material sliding on said rod and urged to seat on the inner partition by a spring abutted against said outer partition, a

nger mounted on said shaft and formed with a rounded slotted end engaged in said cut-out central part of the piston resiliently clamped between said inner partitions, a return duct branched to the cylinder ends and valve means in said duct for communication only from either the one or the other cylinder end to the central cavity.

- 6. A shock-absorber according to claim 5 in which said rod is formed with recessed portions providing leakways through said intake-valves during givenportions of the piston stroke.

7. A shock-absorber according to claim 5, comprising further in combination, axial bored extensions from the inner face of the cylinder plugs receiving the ends of said rod, said rod 10 being shorter than the cylinder to slide in said extensions forming small cylinders in communication withV the main cylinder through metered 8. In a shock absorber, in combination, a body having a bore extending through the same forming a piston-receiving-cylinder, said body havy ing a central cavity communicating with said cylinder intermediate the ends of said cylinder and serving as a liquid supply reservoir, a piston formed with heads, means closing the external ends of said cylinder and forming end chambers in said cylinder in front of said piston heads, a longitudinal rod in said cylinder extending through said piston, intake valves in said heads mounted to slide on said rod and having recessed portions providing leakways through said intake Valves during given portions of the piston stroke.

9. In a shock absorber, further tothe combination claimed in claim 8, end pieces in said cylinder forming for sai-d rod small cylinders in communication with the main cylinder through metered leakports, said rod being adapted to slide longitudinally according to the mean pressure of liquid in said small cylinders whereby it may adapt its positionto the position of balance of the piston.

CHARLES GRANET. MAURICE HELBIG.

References Cited in the i'lle of this patent UNITED STATES PATENISV 

